Evaluation of specific absorbed fractions from internal photon sources in the ICRP Reference Male Phantom

In order to estimate the dose caused by internal radiation, it is necessary to know the specific absorbed fraction (SAF) values; through this work these values have been calculated using the Adult Male Reference Computational Phantom (RCP-AM) from the Publication 110 of the International Commission Radiologic Protection and the Monte Carlo transport code MCNPX. These values were calculated for a combination of 980 pairs of source and target organs, for a total of 12 energies. The results were validated and compared with the results reported by other authors: Hadid et al. (RCP-AM), Petoussi-Henss and Zankl (Golem) and the Oak Ridge National Laboratory (ORNL) stylised model reported by Cristy and Eckerman. Mostly, the SAF values calculated with the RCP-AM do not present significant differences in relation to its previous model Golem. When comparing the SAF values of RCP-AM with that of the ORNL stylised model, huge differences were found. These differences can be explained by the shape of the organs and their relative positions, which are more realistic in the voxelised phantoms.

Harmonization of internal dosimetry procedures in Latin America--ARCAL/IAEA project

Under the auspices of the Regional Coordination Agreement for Latin America, representatives of the eight member states have participated in a project to improve radiological protection for workers exposed to unsealed sources of radiation. The design of the project was based on information obtained from a questionnaire circulated among the participants, from which the initial status of internal dosimetry services in each country was characterised. The objective of the project is to harmonize internal dosimetry procedures, with reference to International Atomic Energy Agency recommendations. After the implementation of new procedures and personnel training, four intercomparison exercises were carried out: measurement of iodine in thyroid phantoms, measurement of gamma emitters in urine samples, measurement of beta emitters in urine samples and internal dose assessments. This project has resulted in important improvements in internal dosimetry services in the region.

A protocol for the calibration of gamma cameras to estimate internal contamination in emergency situations

The concern about accidents involving radioactive materials has led to the search of alternative methods to quickly identify and quantify radionuclides in workers and in the population. One of the options to face up an eventual demand for mass monitoring of internal contamination is the use of a nuclear medicine diagnostic equipment known as gamma camera, a device used to scan patients who have been administered specific amounts of radioactive materials for medical purposes. Although the gamma camera is used for image diagnosis, it can be calibrated with anthropomorphic phantoms or point sources for the quantification of radionuclide activities in the human body. This work presents a protocol for the calibration of gamma cameras for such application. In order to evaluate the suitability of this type of equipment, a gamma camera available in a public hospital located in Rio de Janeiro was calibrated for the in vivo measurement of 131I. The calibration includes the determination of detection efficiencies and minimum detectable activities for each radionuclide. The results show that the gamma camera presents enough sensitivity to detect activity levels corresponding to effective doses below 1 mSv. The protocol is the basis to establish a network of Nuclear Medicine Centres, located in public hospitals in eight countries of Latin America (Argentina, Brazil, Colombia, Cuba, Chile, Mexico, Peru and Uruguay) and in Spain that could be requested to collaborate in remediation actions in the event of an accident involving incorporation of radioactive materials. This protocol is one of the most significant outputs of the IAEA-ARCAL Project (RLA/9/049-LXXVIII) aimed to the Harmonization of Internal Dosimetry Procedures.

Safety and immunogenicity of a killed Leishmania (L.) amazonensis vaccine against cutaneous leishmaniasis in Colombia: a randomized controlled trial

The safety and immunogenicity of an intramuscular (i.m.) and intradermal (ID) formulation of autoclaved Leishmania (Leishmania) amazonensis vaccine was evaluated in 296 volunteers in a randomized, placebo-controlled, double-blind trial in Colombia. There were 4 vaccination groups: i.m. vaccine, i.m. placebo, ID vaccine, and ID placebo. The ID formulations were mixed with BCG as adjuvant at the time of injection. For each group, 3 vaccinations were given with a 20-day interval between injections, and adverse events were monitored at 20 min, and at 2, 7 and 21 days after each injection. BCG-induced adverse reactions resulted in cancellation of the third vaccine administration in the ID groups. Antibody titres did not differ significantly between the groups. Montenegro skin-test conversion was achieved by 86.4% and 90% of the i.m. vaccine group and by 25% and 5% of the i.m. placebo group 80 days and 1 year after vaccination, respectively. A significant increase in mean Leishmania-antigen lymphocyte proliferation indexes was observed after i.m. vaccine immunization, but not after i.m. placebo immunization, 80 days and 1 year after vaccination. Significant levels of IFN gamma but not IL-10 were observed 1 year after vaccination in the i.m. vaccine group compared to the i.m. placebo group. The good safety profile and evidence of Th1 immune reactions due to i.m. vaccination in this phase-I/II study suggest that a population-based phase-III efficacy trial of the i.m. vaccine should be initiated.

Lack of efficacy of mefloquine in the treatment of New World cutaneous leishmaniasis in Colombia

In a nonblinded, therapeutic trial conducted in Colombia, 1.25-1.5 grams of mefloquine base given as a single oral dose or as 250 mg a day for 5-6 consecutive days was not efficacious in the treatment of New World cutaneous leishmaniasis. The drug had cured only 30.8 % of patients with leishmaniasis skin lesions by the 10th week after start of therapy as compared with a 27.9% complete cicatrization rate in historical controls treated with placebo tablets and an 86.3% cicatrization rate in historical controls who received meglumine antimoniate, 20 mg/ kg/day intramuscularly for 20 days, with no upper limit to daily dose. It is concluded that a single course treatment with mefloquine is not indicated as monotherapy in the treatment of Colombian cutaneous leishmaniasis primarily due to L. panamensis.